class Crop

class Crop extends GDImageToolkitOperationBase {
  
  /**
   * {@inheritdoc}
   */
  protected function arguments() {
    return [
      'x' => [
        'description' => 'The starting x offset at which to start the crop, in pixels',
      ],
      'y' => [
        'description' => 'The starting y offset at which to start the crop, in pixels',
      ],
      'width' => [
        'description' => 'The width of the cropped area, in pixels',
        'required' => FALSE,
        'default' => NULL,
      ],
      'height' => [
        'description' => 'The height of the cropped area, in pixels',
        'required' => FALSE,
        'default' => NULL,
      ],
    ];
  }
  
  /**
   * {@inheritdoc}
   */
  protected function validateArguments(array $arguments) {
    // Assure at least one dimension.
    if (empty($arguments['width']) && empty($arguments['height'])) {
      throw new \InvalidArgumentException("At least one dimension ('width' or 'height') must be provided to the image 'crop' operation");
    }
    // Preserve aspect.
    $aspect = $this->getToolkit()
      ->getHeight() / $this->getToolkit()
      ->getWidth();
    $arguments['height'] = empty($arguments['height']) ? $arguments['width'] * $aspect : $arguments['height'];
    $arguments['width'] = empty($arguments['width']) ? $arguments['height'] / $aspect : $arguments['width'];
    // Assure integers for all arguments.
    foreach ([
      'x',
      'y',
      'width',
      'height',
    ] as $key) {
      $arguments[$key] = (int) round($arguments[$key]);
    }
    // Fail when width or height are 0 or negative.
    if ($arguments['width'] <= 0) {
      throw new \InvalidArgumentException("Invalid width ('{$arguments['width']}') specified for the image 'crop' operation");
    }
    if ($arguments['height'] <= 0) {
      throw new \InvalidArgumentException("Invalid height ('{$arguments['height']}') specified for the image 'crop' operation");
    }
    return $arguments;
  }
  
  /**
   * {@inheritdoc}
   */
  protected function execute(array $arguments) {
    // Create a new resource of the required dimensions, and copy and resize
    // the original resource on it with resampling. Destroy the original
    // resource upon success.
    $original_resource = $this->getToolkit()
      ->getResource();
    $data = [
      'width' => $arguments['width'],
      'height' => $arguments['height'],
      'extension' => image_type_to_extension($this->getToolkit()
        ->getType(), FALSE),
      'transparent_color' => $this->getToolkit()
        ->getTransparentColor(),
      'is_temp' => TRUE,
    ];
    if ($this->getToolkit()
      ->apply('create_new', $data)) {
      if (imagecopyresampled($this->getToolkit()
        ->getResource(), $original_resource, 0, 0, $arguments['x'], $arguments['y'], $arguments['width'], $arguments['height'], $arguments['width'], $arguments['height'])) {
        imagedestroy($original_resource);
        return TRUE;
      }
      else {
        // In case of failure, destroy the temporary resource and restore
        // the original one.
        imagedestroy($this->getToolkit()
          ->getResource());
        $this->getToolkit()
          ->setResource($original_resource);
      }
    }
    return FALSE;
  }

}